Add procedurally generated space structures for some epic end-game content to 'wow' in awe to. Megastructures like dyson spheres, ring worlds, planetary orbital rings etc.
Even unfinished megastructures would look epic, like a half completed dyson sphere. Perhaps there could be missions to help complete it.
On a smaller scale, orbital rings would probably fit the size scale in the game better for intractable structures.
They could scale up in size and strength too dependant on the difficulty of the system you travel to.
They would add so much lore to the existing factions, and could have different designs and purposes based on each faction.